A revision of the genus Lasianthus Jack (Rubiaceae) from Vietnam Author Dang, Van-Son 0000-0001-8681-4141 Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & Institute of Tropical Biology, Vietnam Academy of Science and Technology, 85 Tran Quoc Toan Street, District 3, Ho Chi Minh City, Vietnam. & Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Vietnam. & dvsonitb @ gmail. com; https: // orcid. org / 0000 - 0001 - 8681 - 4141 dvsonitb@gmail.com Author Naiki, Akiyo 0000-0002-3235-2823 Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & Iriomote Station, Tropical Biosphere Research Center, University of the Ryukyus, 870 Uehara, Taketomi-cho, Yaeyama-gun, Okinawa, 907 - 1541 Japan. & naiki @ lab. u-ryukyu. ac. jp; https: // orcid. org / 0000 - 0002 - 3235 - 2823 * Author for correspondence naiki@lab.u-ryukyu.ac.jp text Phytotaxa 2023 2023-01-26 581 1 1921 1935 http://dx.doi.org/10.1094/PDIS-04-22-0755-PDN journal article 10.11646/phytotaxa.581.1.1 1179-3163 7571550 50. Lasianthus nghiasonii V.S.Dang & Naiki (2021: 34) — Fig. 77 (plate), Fig. 78 (map) Type: — VIETNAM . Lam Dong Province , Bidoup Nui Ba National Park , 1464 m elev., 26 February 2016 , Tagane S. , Dang V.S. , Nguyen V.N. , Wai J. V 4450 ( holotype VNM ! [ VNM00042919 ]; isotype FU !, VNM ! [ VNM00042920 , VNM00042921 ], the herbarium of Iriomote Station ( Japan )) . FIGURE 77. Lasianthus nghiasonii V.S.Dang & Naiki (from V4450 , VNM): A. Branch with fruit, B. Stipules, C. Abaxial leaf surfaces, D–E. Inflorescence showing side view flower buds, F. Flower, G–H. Fruits, I. Seeds. FIGURE 78. Distribution maps of Lasianthus nghiasonii , L. nhatrangensis , L. ngoclinhensis , L. nuichuaensis and L. oblongilobus . Specimens examined: — VIETNAM . Central : Lam Dong Province , Bidoup Nui Ba National Park , 1464 m elev., 12°10’17.02’’N , 108°41’50.01’’E , in lower montane evergreen forest, 26 February 2016 , Tagane S. , Dang V.S. , Nguyen V.N. , Wai J. V 4450 ( FU , VNM , the herbarium of Iriomote Station ( Japan )); in the same location, 1533 m elev., 12°10’34.07’’N , 108°41’08.04’’E , in lower montane evergreen forest, 21 February 2016 , Tagane S. , Nagamasu H. , Naiki A. , Dang V.S. , Nguyen V.N. , Hoang T.B. , Wai J. V 3987 ( FU , VNM , the herbarium of Iriomote Station ( Japan )); in the same location, 1438 m elev., 12˚10’23.01”N, 108˚41’52.20’’E, 26 November 2017 , in moist evergreen forest, Naiki A. & Dang V.S. 10101, 10102, 10103 ( VNM , the herbarium of Iriomote Station ( Japan )). Khanh Hoa Province , Hon Ba Nature Reserve , 1521 m elev., 12°07’01.82’’N , 108°56’43.63’’E , in evergreen forests, 25 November 2014 , Toyama H., Tagane S. , Dang V.S. , Nagamasu H. , Naiki A. , Tran H. , Yang C.J. with Hieu H.N.P. V2167 ( FU , VNM , the herbarium of Iriomote Station ( Japan )); in the same location, 1502 m elev., 12°07’08.12’’N , 108°56’30.03’’E , in evergreen forests, 15 June 2019 , Dang V.S. , Dang 348 ( VNM ) . Distribution: —Endemic to Vietnam (known from the Bidoup Nui Ba National Park in Lam Dong Province and the Hon Ba Nature Reserve in Khanh Hoa Province ). Habitat & Ecology: —Moist evergreen forest at around 1400–1600 m elev. Phenology: —Flowering and fruiting from February to November. Vernacular name: —Xú hưƠng hoàng nghĩa sƠn. Notes: — Lasianthus nghiasonii is similar to L. inodorus Blume (1826: 998) in the shape of leaves, number of secondary veins, and inflorescence type , but differs from the latter in having longer petioles ( 10–15 mm long vs. 6–10 mm long), bracts 1–2 mm long (vs. 3–6 mm long) and larger calyx tubes ( 3–4 mm long vs. 2 mm long) and fruit color when ripe.